I have dealt with Midland Collections in San Diego, CA and they hare ruthless and horrible. My best advise to you if you owe the money is to send them a Paid and Delete letter and see if that works. If not, my advise is to PAY UP ASAP as they continue to call you constantly and are extremely rude.
I paid my off and it took about 30 days for them to post correctly to my CR.
Good Luck.